Centrifugal compressor



J. s. ALFORD June 5, 1945.

'CENTRIFUGAL COMPRESSOR Filed March 31, 1944 Inventor- Joseph S.A|For'd," b r/ 0AM! His Attorney Patented June 5, 1345 UNITED STATES EPATENT OFFICE OENTRIFUGAL COMPRESSOR Joseph S. Alford, Nahant, Mass assignor to GeneralkElectric Company, a corporation of New Yor Application March 31, 1944, Serial No. 528,900

4 Claims. (Cl. 230-127) The present invention relates to centrifugal of b. plurality of bolts 25. The inner half 23 compressors having an, impeller, and a diffuser has a central Substantially cylindrical portion which is seated on and secured to the com 26 which forms the inlet of the compressor. pressor casing for converting velocity energy Outer portions of the casing halves form a disof a medium impelled by the impeller into prescharge scroll 2! with a flanged discharge consure energy. More particularly, the invention duit ,28. The discharge scroll in the present relates to compressors used as superchargers on example has circumferentially spaced cooling aircraft and operated at high speeds of the order and reinforcing ribs 29. The cross-sectional of 20,000 R. P. M. .Difiiculties have been experiarea of the scroll increases gradually towards enced in the past with compressors having the outlet 28. In the upper part of Fig. 1 this shroudless impellers due to 'hightemperature area is about minimum. Air or like medium and high stresses set up in the casing during impelled by the impeller is conducted to the operation. The casing is ordinarily made in two scroll 21 through a diffuser 30. The difiuser 30 halves bolted together. High stresses set up in has an inner side wall or ring 3|, an outer side the casing have the tendency to force one caswall 32, and a plurality of circumferentially .ing half away from the other, thereby increas- I spaced diffuser vanes 33 integrally formed with ing the clearance between'the free edges of the the side walls 3|, 32. Outer portions of the side impeller blades and the adjacent casing wall, walls 3|, 32 have openings 34, that is, these outer resulting in a substantial reduction of the com portionsbetween adjacent vanes are cut away or pressor 'efliciency and economy. saw-toothed 'in known manner to permit lateral The object of my invention is to provide an as well as radial discharge of air or like meimproved construction and arrangement of cendium from the diffuser into the scroll. The diftrifugal compressors which may be safely operfuser walls have inner cylindrical portions seated ated at high speeds and temperatures without on shoulders 35 and 36 of the inner and outer materially distorting the compressor casing. casing halves 23, 24. The outer diffuser wall 32 For a consideration of what I believe to be has circumferentially spaced bosses 31 for re-' novel and my invention, attention is directed ceiving the inner ends of staybolts 38. These to the following description and the claims apstaybolts have intermediate portions with. collars 'pendedthereto in connection with the accom for accurately spacing the diffuser wall 32 from panying drawing. the outer casing wall 24. Outer portions of the Inthe drawing Fig. 1 illustrates a turbosuperstaybolts are secured to the outer casing 24 by charger for aircraft embodying my invention; means of nuts 39. In addition, a reinforced Fig. 2 is an exploded perspective view of two inner edge portion of the diffuser wall 32 is se- Parts of Fig. 1; and Fig. 3 shows the parts of Fig. cured. to the casing 24 by a row of bolts 40. 2 assembled. v Thus, one wall of the diffuser, in the present The turbosupercharger illustrated by way of example the outer wall, is rigidly secured to and example comprises an exhaust gas-operated supported on the outer casing wall 24. turbine having a nozzle box I with a flanged v According to my invention means are proinlet portion H for receiving exhaust gases. vided for rigidly attaching the inner wall 3| of The gases are discharged from the box I0 "40 the difiuser on the inner casing half 23 inorder through a nozzle structure l2 into a bucket wheel to prevent the inner casing half from moving It which is supported on an-overhun portion away from. the adjacent impeller edges and of a shaft I4. The shaft I4 is rotatably supthereby maintaining a substantially constant ported on a. bearing structure I5 and has another clearanc 4| between said edges and the adoverhung portion to the left of the bearing jacent inner surface of the casing. This is imstructureto which an impeller I6 is secured by portant with regard to shroudless impellers hemeans of a nut I1. The bearing structure l5 cause an increase of said clearance reduces mahas an outer casing forming a spider with arms teriallythe efiiciency of the impeller. Such rigid .|8 supporting the nozzle box ID by means insupport is particularly necessary in compres-v cluding an annular baflle or partition l9 and sors in which the scroll along a part of its cir I bolts 20. The partition l9 also serves to reduce cumference is located inside the outer diameter heat transfer from the box illto the bearing l5. of the impeller. In the drawing it will be noted The centrifugal compressor includes the e that the left-hand upperpart of the scroll is 10- aforementioned impeller. I3 which is driven' by cated outside the outer diameter of the impeller the turbine and has an impeller disk 2| with a In the lower part of the drawing the scroll curves plurality of impeller blades 22 integrally formed inwardly and is partly located substantially intherewith. The impeller is disposed in. a casing side the diameter of the outer part of the imw'hich comprises two halves or walls 23, 24 which peller. In other words, it has an inner diameter with respect to their location on an aircraft may substantially smaller than the outerldiameter of be termed inner and outer halves respectively. the impeller. In the lower part of; the drawing I The two halves are secured together by means the outer wall of the scroll is closely spaced'or directly attached to the inlet conduit at or the casing while in the upper part of the drawing the wall of the scroll is radially spaced from the,

inlet conduit 26. The purpose of curving the scroll gradually inward towards the inlet conduit 26 as its cross-sectional area increases is to keep its over-all outer dimensions at a minimum. With 'such arrangement a portion, sometimes termed a shelf, 42 of the compressor casing 'which forms part of the impeller chamber is not restrained at its outer end by other pertions of the casing from deflecting axially away from the impeller chamber. When subject to high pressure and temperature the irmer casing half or'wall 23 has a tendency to move or buckle away from the impeller; This tendency is especially great with regard to the shelf 42 when unsupported or free at its outer end.

In order to restrain the casing, particularly the shelf portion, from deflecting during operation, means are provided for securely attaching such portion to the inner wall of the diffuser. In the present example the inner casing halfis secured to the inner diffuser wall by a bayonet connection. To this end the inner diflfuser wall 3! is provided with a row of lugs 43 and the inner casing half or wall 23 is provided with a row of cooperating projections having chamfered'edge portions 45 and adapted to flt into grooves 46 formed between the lugs 43 and the inner diiluser wall 3|.

During assembly the casing wall 23 is placed onto the inner difi'user wall 3| with the projections 44 located between the lugs 43. 'Ihereupon the casing half 23 is rotated to move the pro- Jections 44 into the grooves 46 (Fig. 3). With this arrangement the. diffuser is supported and rigidly secured to one casing .half and in turn acts as a' support of the .other casing half, especially the shelf portion thereof,-. preventing deformation of the latter during operation. The bayonet connection between the adjacent portions of the inner difluser wall 3| and the inner casing half also assures a tight joint between these parts during operation, thus preventing-leakage of-fluid through said joint from the discharge scroll into the inlet of thedifiuser.

In the present instance I have shown additional means for stifiening the casing 'in the form of cooperating eccentric annular flanges 41 and 48 t on the outer diffuser wall 32 and the outer casing half 24 respectively. These flanges are machined and abut each other and together with other nortions of the casing form an annular space 49 of varying cross-section. With a tight'fit between the cooperating flanges 41,- 48 there is little leakimpellers and diffusers attached to the wallsof the compressor. One difluser wall is boltedto one casing half of the compressor and the other diffuser wall forms a bayonet connection with the other casing half or wall, preventing the lat ter from moving away from the free edges of the impeller blades, thus maintaining small clearance between the compressor casing and the impeller and also maintaining a tight fit between the diffuser wall and the compressor casing.

Having described the method of operation of my invention, together with the apparatus which Iznow consider to represent the best embodiment ,thereof,v I desire to have it understood; that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Centrifugal compressor comprising a casing having two halves forming an impeller chamber and a scroll, a diffuserhaving' axially spaced walls I secured together, means bolting one of the walls to one casing half, and means forming a bayonet connection between the other wall and an edge portion of the other casing half.

- 2. Centrifugal compressor comprising a casing having two halves forming an impeller chamber and a scroll, having an inner diameter substantially smaller than the outer diameter of the impeller chamber, a shroudless' impeller rotatably disposed in the impeller chamber, a diffuser having axially spaced annular walls and circumferentially spaced vanes integrally formed with the walls, the casing halves having shoulders for supporting the difiuser walls, means bolting one diffuser wall to one casing half, and a bayonet connection between the other diffuser wall and an edge portion of the other casing half. I

3. Centrifugal compressor comprising a casin having an outer and an inner half secured together and forming an. impeller chamber and a I scroll located on opposite sides of the impeller chamber, the inner casing half forming an inlet,

an impeller disposed in the impeller chamber and having a disk with a plurality of circumferentially spaced blades integrally formed thereon and having free edges forming a close clearance with an adjacent wall portion of the inner casing half, a diffuser having outer and inner walls engaging the outer and inner casing halves respectively, bolt means securing the outer diffuser wall to the outer casing half, andbayonet connecting means securing the inner casing half to the inner difage of fluid from the scroll intothe, annular space 7 to reduce leakage of compressed medium from the scroll.

The outer casing half or wall 24 has a plurality of circumferentially spaced bosses ill secured to the arms ID of the bearing I! by means of circumferentially spaced bolts and nuts 8| to supfuser wall. I

4. Centrifugal compressor comprisirfg a casing having an outer and an innerhalf secured together and forming an impeller chamber and a scroll, the inner casing half forming an inlet, an impeller disposed in the impeller chamber and having a. disk with a plurality of circumferentially spaced blades integrally formed thereon and hav-' ing free edges forming a close clearance with an adjacent wall portion of the inner casing half, a

' diffuser located substantially in the scroll and port'the compressor casing on the-spiderof the bearing 1!. 1

Thus, with my invention I have accomplished an improved construction andarrangement of centrifugal type compressors having shroudiess outer edge is restrained having outer and inner walls engaging the'outer and inner casing halves respectively, bolt means securing the outer diffuser wall to thu'outer casing half, and other means securing the inner casing half to the inner diffuser wall, a portion of the scroll having an inner diameter substantially smaller than theouter diameter of the impeller, thus forming a shelf portion which at its radially said other means.

' I JOSEPH S. ALFQRD.

from axial deflection by Patent No 2 ,377 JED h I -cznwmcnm 0F comcnou. I 7 June 5, 1915. 1 JOSEPHS. ALFORD. I fit is hereby certified that error appears; in the prtnted apec1f1at1on of the abovenqmbered patent requiring correction as follows: Page 2,":I1rat" colum 11ne-32, after the word. "the' insert ---inner--; and second column, .11ne'28, claim 2, after "scroll" strike out the comma; and that the acid Letters Patent ahouldbe read with this correction therein that the eeme nmy-constorm to the record of the ceae inthe' Patent Orifice.

Signed and sealed this 25t day of Septanber, A. D. 1915.

Leslie Frazer (Seal) First Assistant camiesi oner of Patents. 

